After he fell, four of Davis’ co-workers quickly pulled him from the tank. One co-worker even waded into the acid to pull him out.

Although Davis was conscious when the EMS team arrived, witnesses told the fire department that Davis had been submerged for a minute. According to Colavitti, Davis appeared to be suffering from shock and his skin showed early signs of acid burns.

“Timing was [of the essence],” Colavitti explained to ABC News of the possible dangers of Davis’ acid burns. “It could be instantaneous or it can [be delayed] depending on the concentration, burns can show up an hour or two hours later.”

Davis was airlifted to the Saint Barnabas Medical Center for treatment and is listed in critical condition.

His co-workers were treated for minor injuries at a local hospital.

Davis was working for the roofing company Gar Con Enterprises. According to the fire department, the roofing company was operating on the premises without a permit.

Gar Con Enterprises did not immediately return calls for comment.

Officials from the Occupational Safety and Health Administration were on the scene to investigate the incident.

Jonathan Wiggs/The Boston Globe via Getty Images(CORPUS CHRISTI, Texas) -- A hydrofluoric acid leak at a Citgo refinery in Texas this week has spurred an additional investigation by the U.S. Chemical Safety Board into the site -- the same site that is already under investigation after a July 2009 fire and explosion released a cloud of the dangerous chemical.

A seven-person team from the CSB began work Wednesday investigating the refinery in Corpus Christi after a leak in the plant's alkylation unit was detected by sensors Monday, automatically setting emergency containment measures. The same unit was responsible for the 2009 leak.

There were no injuries and the community was not in danger, a Citgo spokesperson told ABC News. However, the CSB felt it necessary to launch an additional investigation into the plant "because of the toxic nature of hydrofluoric acid and the need to keep it contained, or to mitigate the consequences of a release," CSB Chair Rafael Moure-Eraso said in a statement.

After the 2009 explosion at the plant, which severely injured one employee and led to another being treated for possible hydrofluoric acid exposure, the CSB issued "urgent safety recommendations" that required Citgo to improve its emergency response system. The CSB said in a report last year that the plant had met those recommendations.

In last year's report, the CSB also estimated that the 2009 accident released around 4,000 pounds of hydrofluoric acid into the atmosphere, although Citgo had initially reported that only 30 pounds had escaped its water containment system.

The amount of chemicals released in this week's accident is not yet available, although a Citgo official said that initial analyses show it contained "a small amount of hydrofluoric acid" in addition to other chemicals.

A joint investigation by ABC News and the Center for Public Integrity that aired on "World News with Diane Sawyer" and "Nightline" last year found that across the country, 50 aging refineries use hydrofluoric acid, putting at risk the 16 million Americans who live within range of its potential spread in the event of an accident.

And around the Citgo refinery in Corpus Christi, which is closely surrounded by residential streets, neighbors told ABC News then that they fear the worst.

"You never know when you go to bed if you're gonna live through the night, or if you have to run through the night," said Janie Mumphord, who lives a few blocks from the plant.

Sen. Patty Murray, D-Wash., told ABC News during the investigation that any plant that uses the acid is "a ticking time bomb."

"Hydrofluoric acid is extremely toxic," Murray said. "It can be deadly immediately to workers around them, it can affect an entire community."